| 摘要 |
A system for detecting and assessing the nature and position of an object passing through, and thus interrupting, one or more beams (13), which system comprises means (14) arranged to generate a matrix of beams (13) intersecting each other, to form a net-like pattern of beams, and means arranged to generate information relating to any beam(s) (13) interrupted by an intruding object and to supply such information to an analyser arranged to determine therefrom, to a suitable approximation, both the nature and position of the object which has interrupted the beam(s) (13).
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